This invention relates to a technique for discharging the remaining propellant in a valve operated pressurized container after the product has been dispensed and also to an advantageous use of that remaining propellant in a particular application.
Hand-held pressurized dispensing containers, and particularly those having a tilt action valve assembly, have been known for a long time. Applicant""s U.S. Pat. No. 5,785,301 is representative of a prior art valve design for use in these pressurized dispensing containers.
The free floating piston that is used in these dispensing containers has a propellant underneath the piston and the product above the piston. In general, the product being dispensed forms a seal between the piston sidewall and the can and thus prevents propellant by-pass. In most cases, the product is forced between the piston sidewall and the can wall during the process of filling the can with the product to be dispensed and this seals the propellant from the product. This is described in greater detail in the U.S. Pat. No. 3,897,672.
When all of the product has been dispensed, the piston is near the top of the can and normally a substantial amount of propellant remains in the can under the piston.
It is desirable that this propellant be discharged prior to disposal of the can so as to minimize such effects as having the can explode.
Furthermore, and from a different point of view, any utility that can be found for this remaining propellant would provide an added value at no additional cost.
Accordingly, it is a major purpose of this invention to provide a technique for readily and simply disposing of the remaining propellant in a pressurized dispensing container after the product has been dispensed.
It is a further purpose of this invention to provide a technique for dispensing the remaining propellant in a fashion that permits use of the propellant in selected situations.
It is also a further purpose of this invention to achieve the above purposes in a fashion that is safe and that provides a can for disposal which is safer than the can with the pressurized propellant.
There are two types of structural techniques that can provide the stop which permits propellant by-pass. Both provide a gap between piston and cap to avoid the sealing line or zone that occurs when the piston tops out on the cap of the can. They are:
1. The use of bumps to form a stop between piston and cap and thus provide the desired gap. This will normally not tilt the piston. Alternatively, an extension on the valve can provide a stop that holds the piston from topping out.
2. The use of a bump or marble in the well of the piston such that engagement with the tilt valve causes the, piston to skew. This provides for a more rapid discharge than when the piston remains orthogonal.
When the piston is caused to skew or tilt, the remaining propellant is discharged in a second or two. When the piston is not skewed but is simply prevented from topping out, the discharge is likely to take five or six seconds. The latter is advantageous when, for example, discharging the remaining propellant in a shaving cream can.
All embodiments of this invention involve a stop that keeps the piston from topping out against the cap. When the piston is stopped and thus not moving, propellant will force its way out around the sidewall of the piston, through the gap formed between piston and cap and out the open valve.
All embodiments release the propellant until the pressure on both sides of the piston is substantially equalized and renders the can safer for disposal.
An embodiment that also skews the piston provides a more rapid discharge of propellant which can be used to clean surfaces to which the product has been applied. Where a tire sealant product has been applied to a tire valve, this permits cleaning the tire valve seat through which the sealant has been inserted so that the tire valve core can be more readily reassembled.
Where the piston is skewed, this invention can be used to provide a gaseous inflation after the dispensing of product. To do such, calls for the inclusion of more of the liquid propellant than would normally be required.